5.2 Typesetting existing music

If you are entering music from an existing score (i.e., typesetting a piece of existing sheet music),

• Enter the manuscript (the physical copy of the music) into LilyPond one system at a time (but still only one bar per line of text), and check each system when you finish it. You may use the showLastLength or showFirstLength properties to speed up processing – see Skipping corrected music.
• Define mBreak = { \break } and insert \mBreak in the input file whenever the manuscript has a line break. This makes it much easier to compare the LilyPond music to the original music. When you are finished proofreading your score, you may define mBreak = { } to remove all those line breaks. This will allow LilyPond to place line breaks wherever it feels are best.
• When entering a part for a transposing instrument into a variable, it is recommended that the notes are wrapped in

  \transpose c natural-pitch {…}
  

  (where natural-pitch is the open pitch of the instrument) so that the music in the variable is effectively in C. You can transpose it back again when the variable is used, if required, but you might not want to (e.g., when printing a score in concert pitch, converting a trombone part from treble to bass clef, etc.). Mistakes in transpositions are less likely if all the music in variables is at a consistent pitch.

  Also, only ever transpose to/from C. That means that the only other keys you will use are the natural pitches of the instruments - bes for a B-flat trumpet, aes for an A-flat clarinet, etc.